This invention relates to a tool wrench assembly for joining and separating segments of a segmented drill pipe in a blasthole drill.
A drilling rig is conventionally used in surface mining and quarrying operations. Many of these rigs are mounted on a vehicle that travels on wheels or tractor crawlers to move the drilling rig to the desired drilling location. Once positioned, a rotary head drives a drill bit to begin the drilling operation.
However, it is impractical for these rigs to have a one-piece drill bit. As these rigs drill deep into the earth, the bit would need to be as long as the deepest possible drill depth. At these lengths, it would be difficult to transport the bits and would require undesirably large masts for support. Moreover, the tip of the drill dulls during use, requiring frequent replacement. It is much more cost effective to replace only the drill tip portion of the drill bit on an as-needed basis.
Hence, most drilling rigs have segmented drill pipe strings. These drill pipe strings include multiple drill pipe segments that are attached together at screw threads. At the lowermost end of the pipe string, the drill bit is attached.
During joining or separation of the drill pipe segments, one of the segments must be held in place while an adjacent segment is rotated to thread or unthread the segments from one another. Typically, a tool wrench engages the flats on the lower segment or otherwise grips it to prevent it from rotating. See e.g., U.S. Pat. Nos. 3,980,143; 5,931,231; 5,996,444; and 6,298,926. See also, U.S. patent publication 2003/0056989. The tool wrench is extended to engage the flats as necessary and is then removed before the drill pipe string is again raised or lowered. The tool wrench may also temporarily support the weight of the drill pipe string when the drill pipe string is not directly attached to the rotary head.
However, particularly during the lifting or withdrawal of the drill pipe segments, an operator may forget to disengage the tool wrench from the flats of the drill pipe segment. This can potentially damage the tool wrench, the components that actuate the tool wrench, and/or the rotary head to which the drill pipe string is attached.
Hence, there is a need for an improved tool wrench assembly. In particular, there is a need for a drilling rig with a tool wrench assembly that is less prone to damage as a result of the inadvertent raising of the pipe string.